PCI Express is a point-to-point architecture and uses a serial data transmission protocol. A single PCI
Express lane consists of four wires and can transmit 250 MB/s in a single direction or 500 MB/s in both
directions simultaneously. This bandwidth is not affected by what is happening on other PCI Express
buses or legacy PCI/PCI-X buses (provided that total bandwidth can be handled by the CPU and the
memory subsystem.) The transmission protocol is somewhat similar to that used for a LAN connection
and contains error correction and detection, packet addressing, and other network features.
PCI Express improves system attributes. PCI Express enables a low-power, scalable, high-bandwidth
communication path with a small number of connections (wires) compared to traditional parallel
interfaces (for example, PCI).
The PCI Express I/O slots can support other PCI Express cards with lesser bus bandwidth than what is
physically defined for the slot. Use the following table to determine compatibility.
For example, a PCI Express x8 card does not work in a PCI Express x1 slot, but a PCI Express x1 card
works in a PCI Express x8 slot.
bandwidth. If a PCI Express x8 card is plugged into the PCI Express x8 slot, the card runs at x4
Slot 4: The HP xw8400 Workstation contains one PCI Express x16 slot that supports x4
bandwidth. If a PCI Express x8 or x16 card is plugged into the PCI Express x8 slot, the card runs
at x4 bandwidth.
PCI Express compatibility matrix for xw8400
PCI Express x1
PCI Express x4
PCI Express x8
PCI Express x16
Removing PCI or PCI Express cards
Disconnect power from the system (
facing up. Remove the PCI retainer
Open the PCI retention clamp by pressing down on the two green clips at the ends of the clamp
(1) and rotating the clamp toward the back of the system.
Chapter 4 Removal and replacement procedures
Slot 3: The HP xw8400 Workstation contains one PCI Express x8 slot that supports x4
(Access panel on page
Pre-disassembly procedures on page
60). Place the workstation on its side with the system board
(PCI retainer on page
71) if present.
55), and remove the